(1) Field of the Invention
This invention generally relates to a device to maintain tightness betweenone or more substrata or structural elements and a fastener, often associated with afastening member running through or anchoring one or more of the structural elements. More particularly, this invention relates to a self-tightening nut system or to a system for rotating a nut or other rotary fastener on the threaded tip of a rod, bolt or similar fastening member, to maintain the tight structural integrity of the fastened structural elements.
(2) Background of Invention
There are many situations requiring application of rotational torque upon a fastener, to maintain the tightness of the fastening long after the initial fastening. One example of such a situation involves the need to tighten a nut fastening two structural elements together after one or both structural elements have shrunken from dehydration. For example, lumber used for construction materials typically contains higher moisture when the structure is first constructed, compared to the moisture content after the structure has been constructed for a period of time. This is especially true when the lumber has been newly treated with preservatives and chemicals to withstand moisture. The internal moisture content of the wood construction elements decreases with the passage of time. This process, along with the compression caused by the weight of the structure bearing down on the wood units, eventually results in the shrinkage of the wood units (sometimes called “settling”). The process is most active during the first couple of years, and can result in a 5-6% decrease in the dimensions of wood units; then the process continues for several more years at a slower rate. As a result, many wooden units attached to each other lose their tight connections, thereby potentially creating a danger during the occurrence of catastrophic events such as hurricanes, tornadoes, strong wind and storms, or earthquakes. Maintenance of the tight connections will reduce or prevent damage caused by the repetitive shaking of the structures during the aforementioned catastrophic events.
Typical construction methods include anchoring the wooden frame of a structure to the footing or foundation of the structure. One such method includes a rod, anchored to the foundation and extending upward through the lower horizontal bottom plate of the wall frame, then continuing upward through the uppermost wooden top plate of the wall frame and terminating in a washer and nut tightened atop the top plate. As the structural frame dries over time, shrinkage/shortening of the wall studs and top plates often results in a gap of at least three-eighths (⅜) inch per floor between the top plate and the once-tight nut. (The weight of the roof and sheetrock also contributes to this gap.) Such gaps enable high winds to vibrate or move the structure or its walls on its foundation; such “play” can damage the structure or, in extreme instances, eventually result in destruction of the structure.
A wide variety of tie-down or take-up systems have been developed to assure that the structural elements remain tightly connected. Known in the art are the following patents and published applications, arguably related to the patentability of the present invention:
U.S. Pat. 1st NamedDate ofNo./application Ser. No.InventorPatent/Publication3,806,992ReimerApr. 30, 19744,721,306ShewchukJan. 26, 19885,364,214FazekasNov. 15, 19945,522,688RehJun. 4, 19965,540,530FazekasJul. 30, 19967,037,060 B2ComminsMay 2, 20062007/0001451 A1StruvenJan. 4, 20072009/0324364SmithDec. 31, 20097,905,066PryorMar. 15, 20112011/0113711 A1EspinosaJul. 20, 2010
U.S. Pat. Nos. 5,364,214 and 5,540,530 issued to Fazekas disclose a self-adjusting tie-down system having a spring as a retainer, rather than to tighten the nut. These patents disclose a pair of opposing wedges that slide relative to each other, to increase in height to occupy any gap that arises between the nut and the top plate.
U.S. Pat. No. 7,037,060 issued to Commins discloses a shrinkage compensator assembly having an internal compression spring interposed between an innermost base cylinder and an outer sliding cylinder, to urge the sliding cylinder upward to increase the height of the assembly.
U.S. patent application Publication Ser. No. 11/447,637 filed by Stuven discloses a spring loaded nut for retaining a tubing connection with the tapered end of a vessel fitting. A compression spring within the nut housing biases a ferrule to maintain the tubing in tight engagement with the tapered end of the vessel fitting, to prevent leakage from the vessel through the fitting.
U.S. patent application Publication Ser. No. 12/309,547 issued to Smith discloses a self-adjusting shrinkage compensation device having four nut segments around a threaded rod, and coiled spring members flexibly holding the segments against the rod.
None of the above listed patents expressly discloses a device for tightening the rotary fastener (such as a nut) on the threaded tip of the fastening member (such as a threaded rod), for maintaining a tight connection between the structural element(s) associated with the rotary fastener and the fastening member, wherein said device includes a spring-powered tightening means applying rotational force directly to a coupling means for rotating the rotary fastener.